The number 74 can be factored as 2(37), so 74 is said to have two distinct prime factors. How many distinct prime factors does 210 have?
We know that $210 = 10 \cdot 21$. Breaking down these factors even further, we have that $10 = 2 \cdot 5$ and $21 = 3 \cdot 7$, so $210 = 2 \cdot 3 \cdot 5 \cdot 7$. Since these factors are all prime, $210$ has $\boxed{4}$ distinct prime factors.